The present invention generally relates to a time division multiple access (TDMA) communication system and, more particularly, to a circuit for measuring carrier power to noise power ratio in a TDMA transmission channel in which a nonlinear signal processing element exists.
With the progress of digital communications technology, TDMA communication systems utilizing satellites have come to be extensively used. Constant monitoring of the quality of a communication channel is of primary concern from the standpoint of channel maintenance and channel quality. The carrier power to noise ratio is one of the items to be monitored for the above purpose and has heretofore been measured in the prior art by measuring carrier power and noise power with a power meter.
The problem with the prior art method which relies on the power meter as stated above is that a true CN ratio cannot be measured due to nonlinearity of characteristics which is particular to a satellite transponder, as will be described later in detail.